DEL MAR – You can see them from northbound Interstate 5 near Via de la Valle. About 20 workers and 15 pieces of heavy equipment are rearranging the landscape as part of the first phase of a three-year, $86 million restoration of the San Dieguito Lagoon.

DON KOHLBAUER / Union-Tribune

This is the area near the fairgrounds where the boardwalk will start. Work is under way on restoration of the San Dieguito Lagoon. The pace of the construction will pick up after the first of the year.

The people and machines will grow by about a third once the pace of construction picks up after the first of the year, said project manager Jon Ruth of Marathon Construction in Lakeside, the contractor.

When work ends between late 2008 and mid-2009, the 440-acre wetland, degraded by time and urban encroachment, will support a population of fish, crabs, birds, small mammals and native plants.

The wetland will have more than a mile of earthen berms to control flooding along the San Dieguito River, plus 115 acres of new tidal salt marsh, and five nesting sites for the endangered California least tern and the Western snowy plover.

Marathon began preparing the site and bringing in the heavy equipment in August. Workers are clearing brush and removing topsoil to be used when the lagoon topography has been rearranged.

Among the things they have been cautioned to watch for are rattlesnakes, ticks, wild animals, dead animals and some open pits near the old Navy airfield off Grand Avenue near the south end of Jimmy Durante Boulevard. Groups of homeless people also have been known to gather in the area.

Marathon Construction's portion of the project encompasses about 330 acres, Ruth said. Southern California Edison is restoring the lagoon to compensate for the loss of fish eggs and larvae at its San Onofre Nuclear Generating Station 33 miles to the north, and it has yet to award the contract for the project's final phase – dredging the mouth of the San Dieguito River and opening it on a permanent basis.

To Ruth, the lagoon restoration is “a big dirt-moving job with a landscaping plan.”

“The moving of the dirt isn't the big issue on the job. Mostly it's making sure everything is going exactly to plan and complying with all the environmental concerns. That's the big challenge.”

Monitors working for the California Coastal Commission, Southern California Edison, and the San Dieguito River Park Joint Powers Authority are keeping a close watch as work proceeds. The wetland is the western terminus of the 55-mile San Dieguito River Park that stretches from Volcan Mountain near Julian to the beach at Del Mar.

“We have a lot of eyes looking at us,” said Joe Ellis, the project superintendent.

Several grinding stones called manos (Spanish for “hands”) have been been uncovered since work began, although not the stone bowls, or metates, that go with them, said Russ Collett, an archaeology monitor for Recon Environmental of San Diego.

The artifacts were used for grinding grain by the Indians who once lived in the area, Collett said. He estimated that they were at least 3,000 years old, and the find was not unexpected.

“These are the same things that we encountered at the site during the digging prior to the project,” Collett said.

All told, about 2 million cubic yards of earth will have been moved around the lagoon by the time construction ends, Ruth said.

Ground levels will be raised in some areas with excavated dirt, and then covered with the stockpiled topsoil. The new grasslands will be planted with native plant species, including cordgrass, red sand verbena, pickleweed, goldfield and tarplant.

The biggest of the flood-control berms, along the north side of the river east of Interstate 5, will be built with more than 500,000 cubic yards of earth, faced by quarter-ton blocks of rock, Ellis said.

About 150 tons of rock removed during construction of the South Bay Freeway have been taken to the lagoon by the California Department of Transportation for the berm, he said.

“We've been doing this kind of work for years,” Ellis said. “But this is the big one.”